Coil housing for a brushless fan

ABSTRACT

A coil housing for a stator in a brushless fan is adapted to reduce the effect of permanent magnets in the fan when power is secured to the fan. The coil housing with an upper and lower case. Each case has multiple radial L-shapes protrusions that hold the coil in position. Each protrusion has a foot perpendicular to the cases. Adjacent feet are separated by an actual distance and a virtual distance. Each foot has edges configured to minimize the virtual distance between adjacent feet so individual magnets in the ring of magnets in the fan do not act on a single foot.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a coil housing for a brushlessfan, and more particularly to a coil housing that is not held assecurely in one position by the permanent magnets when power has beensecured to the brushless fan.

[0003] 2. Description of Related Art

[0004] With reference to FIGS. 7 and 8, a conventional brushless fancomprises a blade assembly (20), a stator (40), a circuit board (60) anda fan housing (80). The circuit board (60) is securely mounted on thefan housing (80). The stator (40) comprises a coil housing (notnumbered) and an annular coil (45). An upper case (41) and acomplementary lower case (43) form the coil housing. The annular coil(45) is mounted between the upper case (41) and the lower case (43). Thestator (40) is securely attached to the circuit board (60). When thestator (40) is powered up, electricity applied to the stator (60)induces an electromagnet in the coil (45) in the stator (40), magnetizesthe upper case (41) and the lower case (43) with opposite polarity andcauses the blade assembly (20) to rotate. The blade assembly (20)comprises multiple blades (not numbered), a hub (not numbered), acentral shaft (10) and a cylindrical permanent magnet (21). The centralshaft (10) extending from the hub rotatably extends through the stator(40). The cylindrical permanent magnet (21) has multiple magneticelements (not numbered).The permanent magnet (21) are formed in a ringthat is mounted in the hub of the blade assembly (20). A conventionalbrushless fan stator (40) has multiple L-shaped protrusions (411, 431)extending from the upper case (41) and the lower case (43). Eachprotrusion (411, 431) has a foot (not numbered) that is perpendicular tothe upper and lower cases (41, 43) and parallel to the magnet elements.When the external power to the fan is interrupted or secured, the magnetelements attract the feet of the protrusions (411, 431) and slow andstop the rotating blade assembly (20). When the blade assembly (20)stops rotating, the magnet elements attract a corresponding foot andhold the blade assembly (20) in place. To start the electric fan, moreelectrical current must be applied to the blade assembly (20) toovercome the magnetic attraction between magnet elements in the bladeassembly (20) and the feet of the protrusions (411, 431) in the stator(40). The increased electrical current when starting the brushless fanreduces the life of the brushless fan and ultimately may represent anelectrical hazard.

[0005] To overcome the shortcomings, the present invention provides acoil housing with protrusions on the upper and lower cases to mitigatethe aforementioned problem.

SUMMARY OF THE INVENTION

[0006] The main objective of the invention is to reduce the ability ofpermanent magnets in the blade assembly to hold the protrusions on theupper and lower cases of the coil housing of a brushless fan in oneplace. When the brushless fan is operating, an attractive force existsbetween feet on protrusions around the edge of the stator and thepermanent magnets of blade assembly. The shape of the protrusions andfeet mitigate the ability of the attractive force to resist the rotationof the blade assembly. Therefore, the magnetic attraction between thefeet and the permanent magnets has less tendency to slow, stop or holdthe blade assembly when power is interrupted.

[0007] Other objectives, advantages and novel features of the inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is an exploded perspective view of a brushless fan with astator and a first embodiment of a coil housing in accordance with thepresent invention;

[0009]FIG. 2 is perspective view of the stator in FIG. 1;

[0010]FIG. 3 is a top plan view of the stator in FIG. 1 mounted in a hubof the blade assembly;

[0011]FIG. 4 is a perspective view of a stator for a brushless fan witha second embodiment of a coil housing in accordance with the presentinvention;

[0012]FIG. 5 is a perspective view of a stator for a brushless fan witha third embodiment of a coil housing in accordance with the presentinvention;

[0013]FIG. 6 is a perspective view of a stator for a brushless fan witha fourth embodiment of a coil housing in accordance with the presentinvention;

[0014]FIG. 7 is an exploded perspective view of a conventional brushlessfan; and

[0015]FIG. 8 is a cross sectional side plan view of the conventionalbrushless fan in FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0016] With reference to FIGS. 1 through 3, a brushless fan comprises afan housing (90), a circuit board (70), a stator (50A) and a bladeassembly (30).

[0017] The blade assembly (30) consists of multiple fan blades (notshown), a cylindrical permanent magnet (31), a hub (32) and a centralshaft (10). The cylindrical permanent magnet (31) has multiple magneticelements (not numbered) and is mounted in the hub (32) of the bladeassembly (30).

[0018] The stator (50A) comprises a coil housing (not numbered), anannular coil (55) and a bearing device (57). The coil housing has anupper case (51) and a lower case (53). The coil (55) is mounted insidethe coil housing between the upper and the lower cases (51,53), and theannular coil (55) have an exterior radius. The upper case (51) and thelower case (53) are circular with a center (not numbered) and a throughhole (not numbered) formed at the center through which the bearingdevice (57) is mounted. Multiply protrusions (511A, 531A) with a distalend and a proximal end extend radially from the upper and lower cases(51A, 53A). The protrusions (511A, 531A) respectively correspond toalternate electromagnetic poles generated by the coil (55) whenelectrical power is applied to the brushless fan.

[0019] A foot is formed on the distal end of each protrusion (511A,531A) by bending the distal end at a right angle to the protrusion(511A, 531A). Each foot has an arced surface corresponding to theexterior radius of the annular coil (55), a distal edge (not numbered),a proximal edge (not numbered) and a lead and following edge. Adjacentfeet have an actual separation and a virtual or radial separation. Arelatively large actual separation between adjacent feet allows the feetto act as identifiable electromagnetic poles of the stator (50A). Arelatively small virtual or radial separation between adjacent feetensures that no permanent magnet element is ever over a gap betweenadjacent feet.

[0020] With reference to FIGS. 2 and 3, each protrusion (511A, 531A) hastwo radial edges extending from the center of the corresponding case(51A, 53A). At least one of the leading or following edges of each footis an inclined edge (66) to increase the actual separation betweenadjacent feet while minimizing the virtual or radial separation betweenadjacent feet.

[0021] With reference to FIG. 4 or 5, each protrusion (511B, 511C, 531B,531C) has two radial edges extending from the center of thecorresponding case (51B, 51C, 53B, 53C). If the inclined edge (66) of afoot on the upper protrusion (511B, 511C) is the leading or followingedge, the inclined edge (66) of a foot on the lower protrusion (531B,531C) is the following or leading edge depending on the rotationaldirection. At least one of the leading and following edges of each footis an inclined edge (66) to increase the actual separation betweenadjacent feet while minimizing the virtual or radial separation betweenadjacent feet.

[0022] With reference to FIG. 6, each protrusion (511D, 531D) has tworadial edges extending from the center of the corresponding case (51D,53D). Both the leading and following edges of each foot are inclinededges to increase the actual separation between adjacent feet whileminimizing the virtual or radial separation between adjacent feet.

[0023] In all other aspects, the brushless fan is conventional, andfurther description of the convention features is not included.

[0024] The circuit board (70) is securely attached to the stator (50A),and the stator (50A) is securely mounted in the fan housing (90).

[0025] The central shaft (10) rotatably extends through the bearingdevice (57) in the stator (50A), and the bearing device (57) allows thecentral shaft (10) rotate freely.

[0026] With reference to FIGS. 2 through 6, the stator (50A-D) has fourembodiments comprising multiply protrusions (511A-D, 531A-D), and themultiply protrusions (511A-D, 531A-D) have feet with various inclinededges (66) in each embodiment. As the brushless fan is powered up, theprotrusions (511, 531) on the upper and lower case (51, 53) formalternative magnetic poles to attract or to repel the annular permanentmagnet (31) in the blade assembly (30). Therefore, the blade assembly(30) rotates when power is applied. When power is interrupted during theoperation of the brushless fan, the blade assembly (30) stops but is notheld in a fixed position because the permanent magnet elements do notuniquely align with the individual feet. The inclined edge(s) (66) ofthe feet on the multiple protrusion's (511A-D, 531A-D) lower the effectof the magnetic attractive force on the individual feet since thepermanent magnet elements easily overlap adjacent feet. Because thepermanent magnet elements overlap adjacent feet on the multipleprotrusions (511A-D, 531A-D), the blade assembly (30) easily rotateswhen power applied.

What is claimed is:
 1. A coil housing for a brushless fan that includesa fan housing, a circuit board, a stator and a blade assembly; where theblade assembly includes a central shaft that rotatably extends throughthe stator; and the stator includes a bearing device through which thecentral shaft of the blade assembly rotatably extends; the coil housingcomprises; an upper case, which is circular with a center, adapted to besecurely mounted on the bearing device and having multiple radialprotrusions extending from the center of the upper case; multiple upperfeet respectively extending from the multiple protrusions of the uppercase; each upper foot has at least one inclined edge; a lower case,which is circular with a center, connected to the upper case and adaptedto be securely mounted on the bearing device, and having multiple radialprotrusions extending from the center of the lower case; and multiplelower feet respectively extending from the multiple protrusions of thelower case; each lower foot has at least one inclined edge to increasean actual separation between adjacent upper feet on the upper case whileminimizing a virtual or radial separation between adjacent feet.
 2. Thecoil housing as claimed in claim 1, wherein each upper foot has aleading edge and a following edge opposite to the leading edge; eachupper foot has one inclined edge formed on the leading edge of the uppercase; each lower foot has a leading edge facing the following edge of anadjacent upper foot and a following edge opposite to the leading edge ofthe lower foot and facing the leading edge of an adjacent upper foot;and each lower foot has one inclined edge formed on the leading edge ofthe lower case.
 3. The coil housing as claimed in claim 1, wherein eachupper foot has a leading edge and a following edge opposite to theleading edge; each upper foot has one inclined edge formed on theleading edge of the upper case; each lower foot has a leading edgefacing the following edge of an adjacent upper foot and a following edgeopposite to the leading edge of the lower foot and facing the leadingedge of an adjacent upper foot; and each lower foot has one inclinededge formed on the following edge of the lower case.
 4. The coil housingas claimed in claim 1, wherein each upper foot has a leading edge and afollowing edge opposite to the leading edge; each upper foot has oneinclined edge formed on the following edge of the upper case; each lowerfoot has a leading edge facing the following edge of an adjacent upperfoot and a following edge opposite to the leading edge of the lower footand facing the leading edge of an adjacent upper foot; and each lowerfoot has one inclined edge formed on the leading edge of the lower case.5. The coil housing as claimed in claim 1, wherein each upper foot has aleading edge and a following edge opposite to the leading edge; eachupper foot has one inclined edge formed on the following edge of theupper case; each lower foot has a leading edge facing the following edgeof an adjacent upper foot and a following edge opposite to the leadingedge of the lower foot and facing the leading edge of an adjacent upperfoot; and each lower foot has one inclined edge formed on the leadingedge of the lower case.
 6. The coil house as claimed in claim 1, whereineach upper foot has two inclined edges respectively formed on two edgesof the upper foot; and each lower foot has two inclined edgesrespectively formed on two edges of the lower foot.